System of space discharge devices



March 24, 1925. 1,530,981

0. o. CECCARiNE SYSTEM OF SPACE DISCHARGE DEVICES Filed Jan. 25, 1924 Patented Mar. 24, 1925.

UNITED STATES PATENT OFFICE.

OLINDO O. CECCARINI, OF MAHWAH, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

SYSTEM OF SPACE DISCHARGE DEVICES.

Application filed January 25, 1924. Serial NO. 688,389.

To all whom it may concern Be it known that I, ()LINDO O. CnccARiNI, a subject of the King of Italy, residing at Mahwah, in the county of Bergen and State of New Jersey, have invented certain new and useful Improvements in Systems of Space Discharge Devices, of which the following is a full, clear, concise, and exact description.

This invention relates to a space discharge system and more particularly to an arrangement including tandem connected three electrode devices of this type having a substantially uniform transmission characteristic for current components within a definite frequency range.

This invention provides a transmission system including a plurality of tandem connected three electrode space discharge de vices supplied with space current from a common source through an impedance element, the potential drop across which is impressed upon the control electrodes of the devices, and means associated with the impedance element for preventing the production of undesired oscillations, whereby good quality transmission for all current components within the audible frequency range is secured.

In accordance with the embodiment of this invention to be described in detail a plurality of tandem connected space discharge devices are supplied with space current from a variable voltage source through a resistance the voltage drop across which is impressed upon the impedance control electrodes of the devices. The voltage drop across an inductance included in the alternating current output path of the first device is supplied through a condenser to the input electrodes of the succeeding devices of the system. In shunt to the resistance is a network or filter, included in the input circuits oi: the devices, which serves to so limit the amplitude of the fluctuating or alternating current energy fed back from the output circuits to the input circuits of the devices that sustained oscillations are not produced, or singing does not occur,

voltage variations of the source supplying space current to a discharge device from being impressed upon its control electrode. A feature of this invention is the provision of a simple arrangement of this type whereby all current components within the audible frequency range may be substantial- 1y uniformly transmitted without distort-ing the transmitted energy.

For a complete understanding of the present invention reference should be made to the following description read in conjunction with the attached drawing in which the single figure illustrates the invention applied to a radio transmitting system.

Referring to the drawing a circuit 1 represents a source of audible frequency currents to be supplied to an input transformer comprising primary winding 2 and secondary winding 3 the terminals of which are connected to the input electrodes of a space discharge device 4. The discharge device comprises a vessel enclosing a cathode 5, anode 6 and a control-electrode or grid 7. Heating current is supplied to the cathode 5 through a control resistance 8 by a source 9.

Condensers 10' and 11 are connected in series across the terminals of the cathode 5.

Space current is supplied to the discharge device by a source, herein shown by way of example, as a. generator 12, through a resistance 13 and choke coil 14. The resistance 13 serves to determine the voltage at which space current is supplied to the device 4.

Polarizing potential derived from a resistanee 15 included in the lead connecting the negative terminal of the source 12 to the cathode 5, is impressed upon the control electrode 7 and is adapted to limit the operation of the device to the linear portion of its input-voltage-outputcurrent characteristic curve, whereby the current flowing through its output circuit is a replica in amplified form of the audible frequency currents supplied by the circuit 1.

The input circuit of the device 4 may be traced from the cathode 5, condensers 10 and 11, coil 3, grid 7 and across the space within the device to the cathode.

The path for the polarizing potential extends from one terminal of the resistance 15 to the cathode 5 across the space within the amplifier 4 to the grid 7, coil 3 and thence back to the other terminal of the resistance 15.

The space current path of the device 4 may be traced from the positive terminal of the source 12, resistance 13, choke coil 14, anode 6 across .the space within the device to the cathode 5, resistance 15 to the negative terminal of the source 12.

The output path for amplified currents of audible frequency may be traced from the anode 6, through the coil 14, the by-pass condenser 16 to the cathode 5, and across the space within the device to the anode 6.

The output circuit of the amplifier is provided with an additional alternating current path including a condenser 17 and a resistance 22. The alternating current po tential drop across the combination of choke coil 14 and resistance 22 is impressed upon the input electrodes of a second three-electrode space discharge device 18.

The device 18 is the modulator or variable impedance element of a system for producing modulated carrier waves, similar to that disclosed in Patent 1,442,147, January 16, 1923 to Heising. This system comprises the modulator 18 and oscillator 19 herein shown as three-electrode space discharge devices having their anodes connected through a high inductance choke coil 20 to the positive terminal of the source 12. As described in Patent 1,442,147 the source 12 and choke coil 20 constitute asource for supplying substantially constant space current to the parallel connected devices 18 and 19. The input and output circuits of the device 19 are coupled in feed-back relation to generate high frequency waves in the antenna circuit 21 the constants of which serve. in general, to determine the frequency of the waves generated.

Vith the modulator-oscillator arrangement described above a carrier wave having its amplitude modulated in accordance with the audible frequency energy impressed, by the amplifier 4, upon the input circuit of the modulator 18 is produced and supplied to the antenna. For a detailed description of the operation of the system for producing modulated carrier waves, reference may be had to the above mentioned patent.

The voltage drop across the resistance 15 is impressed, through the circuit including the resistance 22, upon the impedance control electrode of the modulator 18 to polarizc it. The path for the polarizing potential may be traced from the upper terminal of resistance 15 to the cathode and across the space within the device 18 to its grid, through the resistance 22 to the lead connecting the lower terminal of coil 3 to the lower terminal of resistance 15.

Space current is supplied to the modulator by the source 12 through a path extending from the positive terminal of the source through the coil 20, across the space to its cathode and resistance 15 to negative terminal of the source 12.

The source 12 is shunted by a by-pass condenser l6 which primarily operatcs to suppress variations in the voltage supplied by the source 12. These variation occur at a rate correspondin to certain tones of the audible range and hence the condenser 16- will serve as a low impedance path for alternating currents of frequencies corresponding to these variations and high frequencies, while audible frequency currents of lower frequencies will flow through the source 12. The alternating current output circuit of device 18 may be traced from the anode, coil 20, condenser 16 or source 12, resistance 15 to the cathode and across the space path within the modulating device to its anode.

The oscillating device 19 is provided with a leak path comprising a resistance 24 and a condenser 23 connected in parallel. High frequency current is prevented from traversing the circuit of the modulator by the coil 25 and the output circuit of the oscillator 19 includes a condenser 26 which provides a low impedance for the high frequency current from its anode to its cathode. The variable condenser 31 serves to regulate the power factor of the high frequency current flowing through the anode circuit of the oscillator. Heating current is supplied to the cathodes of the devices 18 and 19 by the source 9 through adjustable resistances 27 and 28. I

By properly selecting the capacity value of condenser 17 and inductance 14 the coupling between the amplifier 4 and modulator 18 may be given a transmission characteristic which is uniform for all frequencies within the audible frequency range.

The resistance 15 is included in the input circuit of the amplifier and also in a common portion of the input and output circuits of the modulator 18 and hence serves as an element coupling these circuits.

Since the element 15 is included in the alternating current path of the modulator 18 any amplified current flowing therethrough develops across this element a difference of potential which is impressed upon the control electrodes of the devices 4 and 18.

In practice it has been found that at times the fluctuating or alternating current energy fed back through the resistance 15 is of sufficient amplitude and in proper phase relation to the energy transmitted through the system to cause the system to sing, or in other words to produce sustained oscillations, which not only distort but, under certain conditions actually interrupt the transmission of waves through the system.

To prevent distortion and mutilation of the audible frequency currents, while permitting the use of the system described above tor uniformly transmitting all current components within the audible frequency range,

the input circuit is provided with a filter or network connected in parallel with the resistance 15. The filter comprises a resist ance 29 and a condenser 11 connected in scies. One terminal of the resistance 2 is tonnected to one terminal of the rcsistanrc while the other terminal of 29 is cornzecicd to the lead extending from the one terminal of the coil 3 to the common connection for the adjacent plates of the condensers 10 and 11, the other plate of the condenser ll.

' alternating current that the energy fed back is insuflicient to cause singing in the sys tern. (The resistance condenser filter 29, 10, 11 dlso serves to efficiently exclude from the input circuit any fluctuations flowing from the source 12 through the resistance 15 which may not have been wholly suppressed by the condenser 16. It is preferred to use a resistance as the series arm of the filter rather than an inductance, since it renders the filter aperiodic. There is no loss of useful energy in the resistance 29 be cause of the fact that substantially no current flows through this resistance except the fluctuations which are to be suppressed.

Tests have been made with a radio transmitter provided with the above described system including a space discharge amplifv ing device a having an internal impedance of the order of 5.000 ohms supplied with space current at 1,600 volts througha path including a resistance of 10,000 ohms. an inductance of 40 henries and a resistance 15 of the order of ohms for determining the polarizing potential impressed upon the control electrode of the device. A condenser 16 of 2 m. f. capacity was included in the alternating current output circuit, in shunt to the space current source. The network in shunt to the 7 5 ohm resistance consisted of a resistance 29 of the order of 1,500 ohms, and the two condensers 10 and 11 in series across the cathode of the device were each of 3 m. f. capacity.

The potential drop across the inductance in the output circuit of the amplifier 4 due to the flow of audible frequency current thcrethrough was impressed tilt-rough a condenser 17 of 1 m. f. capacity upon the control electrode of the modulator 18. comprising two arallel connected space discharge devices each having an impedance of the order of 5,000 ohms. Space current was supplied at 1.600 volts through a choke co l 20 of eight henries to the modulator oscillator. The oscillator consisted of two parallel connected discharge devices 19. The alternating circuit output paths of the amplifier and the modulator each included a condenser. 16 and 16 respectively, of 2 m. f capacity in shunt to the space current source.

Af'radio transmitter having the constants given above was used for broadcasting and the space discharge system, comprising the amplifier and modulator, transmitted with substantially uniformly good quality and without distortion all current components corresponding to speech as well as the tones produced by different musical instruments from the lowest to the highest notes used in musical compositions.

From the preceding description it will be seen that the present invention provides an arrangement of tandem connected space discharge devices having the potential impressed upon their control electrodes detern'iined by the flow of space current. which is adapted to effect the desired uniform amplification of all current components within the audible frequency range substantially without distortion or mutilation.

Although a system has been described including two tandem connected space discharge dcvices. it is to be understood that the principles of this invention may be ap plied to a system comprising any number of similarly connected devices.

lVhile certain circuit arrangements and specific details have been described above for the purpose of completely and clearly disclosing the principles of the invention, it is to be understood that this invention is not limited to the specific features disclosed but only by the scope of the attached claims.

W'hat is claimed is:

1. An electrical system comprising a plurality of tandem connected three electrode space discharge devices, means included in the circ zit associated with the devices through which space current flows for determining the potential impressed upon the control electrodes of said devices. and means associated with said potential determining means for preventing distortion of the waves supplied by said system to a load circuit.

2. An electrical system comprising a plurality of tandem connected three electrode space discharge devices, a source of space current therefor, an impedance element through which space current flows for determining the potential im ressed upon the control electrodes of said evices', and means associated with said impedance element for preventing distortion of the waves supplied by said system to aload circuit.

3. An electrical system comprising aplurality of tandem connected space discharge devices, a space current circuit for said devices including means for determining the polarizing potential impressed upon the control electrodesof said devices and means associated With said potential 'determi ing means but external to said space current circuit for preventing distortion of the waves supplied by said system to a load circuit.

4. An electrical system comprisinga plurality of tandem connected space discharge devices, a space current circuit for saiddevices including means for determining the polarizing potential impressed upon the control electrodes of said devices, and means comprising impedance elements of different characteristics associated with said potential determining means for preventing distortion of the waves supplied by said system to a load circuit.

5. An electrical system comprising a plurality of tandem connected space discharge devices, a space current circuit for said devices including an impedance element for determining the polarizing potential impressed upon the control electrodes of said devices, and means comprising impedance elements of different characteristics associated with said first mentioned impedance element for preventing distortion of the waves supplied by said system to a load circuit.

6. An electrical system comprising a plurality of tandem connected three electrode space discharge devices, a source of space current therefor, a resistance through which space current flows, means for impressing the potential drop across said resistance upon the control. electrodes of said devices, and means associated with said impedance element for preventing distortion of the waves supplied by said system to a load circuit.

7. An electrical system comprising a plurality of tandem connected three electrode space discharge devices, a source of space current therefor, a resistance through which space current flows, means for impressing the potential drop across said resistance upon the control electrodes of said devices, and a network including impedance elements having different impedance characteristics in shunt to said resistance for preventing distortion of the waves supplied by said system to a load circuit.

8. An electrical system comprising a plurality of tandem connected three electrode space discharge devices, a source of space current therefor, a resistance through which space current flows, means for impressing the potential drop across" said resistance upon the control electrodes of said devices, and a filter in shunt to said resistance for preventing distortion ofthe waves supplied by said system to a. load circuit.

9. An electrical system comprising tandem connected three electrode space discharge devices, a source of space current for said devices,. a resistance included in the space currentpath of said devices, an alternating current output path for one of said devices including said resistance, means for impressing the potential drop across said resistance upon the impedance control electrode of said devices, and means associated with said resistance for limiting the coup ling effected thereby for alternating current to a negligible value.

IOeAn' electrical system'v comprising tandem connected three electrode space discharge devices, a source of space current for said devices, a resistance included in the space current path of said devices, an alternating current output path for one of said devices including said resistance, means for 11. An electrical system comprising tan dem connected three electrode space discharge devices, a source of space current for said devices, a resistance included in the space current path of said devices, an alternating current output path for one of said devices including said resistance means for impressing the potential drop across said resistance upon the impedance control electrodes of said devices, and, in shunt to said resistance, a filter for limiting the coupling effect of said resistance for alternating-cur rent to a substantially negligible value.

12. An electrical system comprising a plurality of space discharge devices, means for connecting said devices in tandem adapted to uniformly transfer waves within a definite frequency range, a space circuit source for said devices, a resistance included in the space current circuit of said devices, an alternating current output circuit for one of said devices including said resistance, means for impressing the voltage drop across said resistance upon the impedance control electrodes of said devices, and a network, in shunt to said resistance but external to said space current circuit, for reducing the coupling effect'of said resistance for alternating current-zto a substantially negligible value.

13. An electrical system comprising a plurality of space discharge devices, means for connecting said devices in tandem adapted to uniformly transfer waves within a definite frequency range, a space circuit source for said devices. a resistance included in the space current circuit of said devices, an alternating current output circuit for one of said devices including said resistance, means for impressing the voltage drop across said resistance upon the impedance control electrodes of said devices, and a filter, in shunt to said resistance but external to said space current circuit, for reducing the coupling effect of said resistance for alternating current to a substantially negligible value.

14. An electrical system comprising a plurality of space discharge devices, means for com'iecting said devices in tandem adapted to uniformly transfer waves within the audible frequency range, a space circuit source for said devices, a resistance in cluded in the space current circuit of said devices, an alternating current output circuit for one of said devices including said resistance, means for impressing the voltage drop across said resistance upon the impedance control electrodes of said devices, and a filter in shunt to said resistance external to said space current circuit for reducing the coupling effect of said resistance for alternating current to a substantially negligible value.

15. An amplifying system comprising a plurality of tandem connected space discharge devices each having a cathode, an anode, and an impedance control electrode, means for supplying space current to said devices through an impedance element, the voltage drop across which is impressed upon the control electrodes of said devices, the alternating current output circuit of said devices, except the first, including said inr pedance element, and means associated with said impedance element for preventing distortion of the amplified energy.

16. An amplifying system comprising a plurality of tandem connected space discharge devices each having a cathode, an anode, and an impedance control electrode, supplied with space current through an impedance element, the voltage drop across which is impressed upon the control electrodes of said devices, said impedance element being external to the alternating current output circuit of the first of said devices but included in the alternating current output circuit of the other of said devices, and means associated with said impedance element for preventing singing in said system.

17. An amplifying system comprising a plurality of tandem connected space discharge devices each having a cathode, an

anode, and an impedance control electrode, means for supplying space current to said devices through a resistance the voltage drop across which is impressed upon the control electrodes of said devices, said resistance being external to the alternating current output circuit of the first of said devices but included in the alterating cur rent output circuit of the other of said devices, and a network in shunt to said resistance for preventing singing in said system.

18. The combination of a space discharge device, means for supplying current to be amplified to said device, means for determining distortionless operation of said device, and a condenser-resistance filter associated with said determining means.

19. The combination of a space discharge repeater having an impedance control electrode, means included in the output circuit of said repeater for impressing a negative potential upon said control electrode of such value that said device operates without distorting current repeated thereby, and a resistance condenser filter network between said means and said electrode.

20. The combination of a space discharge device including an impedance control elec trode, an input circuit through which variable current to be amplified is supplied to said device, a source supplying to said electrode a negative potential of such value that said device operates without distorting the variable current and a resistance condenser network between said source and said electrode.

21. The combination of a space discharge device having a cathode and a grid, a circuit connecting said cathode to said grid through which current to be amplified is supplied to said device, means for impressing upon said grid a potential of such value that said device amplifies without distorting the variable current supplied thereto, and a resistance-condenser filter connected across said potential impressing means.

22. The combination of a space discharge device having a cathode and a grid, a circuit connecting said cathode to said grid through which current to be amplied is supplied to said device, means for impressing upon said grid a potential of such value that said device amplifies without distorting the variable current supplied thereto. and a resistance-condenser filter connected in parallel with said potential impressing means.

23. An electron discharge device having a cathode, an anode and a control electrode, a source of space current between said cathode and anode, an impedance in circuit with said source, a connection from said impedance to said control electrode for supplying a steady potential thereto, a resistance in said connection and a condenser connecting the cathode to said resistance at a point remote from said impedance.

24. The combination of a space discharge device, an input circuit and an output-circuit therefor, a network associated with said circuits having an impedance common to both circuits, an element of relatively high impedance for output current in series with said common impedance and an element of low impedance for shunting output current from said other impedances.

25. The combination of a space discharge device having a cathode, an anode and a grid, an input circuit and an output circuit therefor, an output current path including an impedance common to said circuits, 0. high impedance in series with said common impedance and a shunt path of low impedance to output current between said impedances and the output electrodes.

26. An electrical system comprising a space discharge device, an input circuit and an output circuit therefor, an impedance common to said circuits, said output circuit including a shunt path for output current between said common impedance and said device, and means associated with said common impedance and said shunt path tending to cause output current to flow through said shunt path.

27. An electrical system comprising a space discharge amplifier having input and output circuits, an impedance common to said input and output circuits, a path of low impedance foramplified current connected 1 to one terminal of said common impedance. a path of low impedance for fluctuating current connected to the other terminal of said common impedance and a relatively high impedance for confinin amplified current and fluctuating current to their respective low impedance paths.

In Witness whereof, I hereunto subscribe my name this 22 day of January, A. D. 1924.

OLINDO O. CECCARIN I.

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